Through-Silicon Via “(hereinafter referred to as TSV) is a 3D packaging technology capable of stacking a plurality of chips vertically in a manner like a sandwich. In order to have a higher finesse of chip stack, silicon interposer is accordingly developed.
FIG. 1 is a schematic cross-sectional view of a common silicon interposer structure known in prior art. As shown, a plurality of TSV structures 100 (herein in FIG. 1 is exemplified by two TSV structures 100 only) are formed in a silicon substrate 10, and a dielectric layer 102 and a re-distribution layer (hereinafter referred to as RDL) 101 with specific patterns are formed on one side of the silicon substrate 10. Specifically, the TSV structure 100 is used to provide a via so that the components and/or chips (not shown) disposed on top and bottom of the silicon substrate 10 can have an electrical connection to each other; and the RDL 101 is used to redistribute I/O pads and thereby enabling the related chips to apply in various component modules.
In the related art, however, the formation of the TSV structures 100 in the silicon interposer is realized by using three masks. Specifically, a first mask is used for the formation of a plurality of shallow trenches on a surface of the silicon substrate 10, wherein these shallow trenches will be used as alignment marks for the follow-up manufacturing process. Next, a second mask, aligned with the aforementioned alignment marks, is used to define a plurality of deep trenches of the TSV structures 100. After the deep trenches are formed by performing one or more etching processes, the TSV structures 100 for electrically connecting the components and/or chips disposed on top and bottom of the silicon substrate 10 are formed by performing a metal filling and at least one planarization process to the deep trenches. Then, a dielectric layer is formed on the substrate 10 and a third mask is used to form trenches for the RDL 101. After the trenches for the RDL are formed, a metal filling and at least one planarization process are performed to finish fabricating of the RDL 101. Therefore, at least three masks and multiple metal filling/planarization processes are required for the formation of the TSV structures 100 and the RDL 101 as taught in prior art or conventional related art, and consequentially the conventional interposer structure has a relatively high manufacturing cost.